In the United States alone, there are approximately thirteen million persons who have diabetes, with about 750,000 new cases diagnosed each year. Total health care costs for diabetes mellitus is about 20 billion dollars per year, representing 5% of the total health care dollar.
Among the many problems that diabetic patients face, foot ulceration is one of the more significant risks. When it occurs, it leads to increased morbidity, amputation rates and mortality. For example, incidents of amputation resulting from ulceration is fifteen times higher than found in the general population. This is primarily because of the poor healing potential seen in the diabetic patient. Ulceration of the foot is multi-factorial in the diabetic population, and among the pre-disposing etiologies are: small vessel disease leading to ease of skin breakdown and poor healing potential; a peripheral neuropathy which makes the foot insensitive to pain; and, in many cases, a suppressed immunologic system.
It has been appreciated for some time that potential pressure areas of the foot can be identified by cast molding or electronic mapping techniques. With this information custom shoes or orthoses can be fabricated which are provided with relieved areas created by contouring that portion of the shoe away from the defined potential pressure areas. However, shoe configurations tend to change with wear and foot shapes vary with modes of force distribution. For example, activity levels, edema and subtle changes in gait pattern create contact in the area that was meant to be protected. Often the patient may be unaware of the change due to the loss of protective sensation. Thus, what was meant to be a protected area actually may ulcerate. Such changes may occur in a brief time frame of only a few hours of wear of the custom shoe.
It will be recognized that similar problems with undue pressure, and the resulting ulceration, may occur with various forms of foot maladies. For example, persons with partially amputated feet often can have undue pressure applied within the shoe, with the locations changing in the same manner as described above. Persons with a club foot or other deformities likewise can have ulceration problems.
A multi-event notification system for monitoring critical pressure points on persons with diminished sensation of the feet is described in U.S. Pat. No. 4,647,918 issued to W. Goforth on Mar. 3, 1987. This system utilizes a plurality of pressure transducers mounted within a shoe for measuring and monitoring pressure at any number of points on a patient's foot. The transducers are electrically connected to a microprocessor that is programmable to integrate the pressure sensed at the sensing points over a preselected time interval. If the integrated pressure at any of the sensing points reaches a preselected threshold over this time interval, an alarm indicator provides an alarm indication that the total number of pressure events exceeds the threshold limit.
Further, there are devices that provide some form of alarm when foot pressure against the bottom of a shoe exceeds a certain threshold. These devices include those described in U.S. Pat. 5,253,654 issued to B. Thomas et al on Oct. 19, 1993, and U.S. Pat. Nos. 5,269,081 and 5,357,696 issued to the present inventors on Dec. 14, 1993 and Oct. 25, 1994, respectively. These patents, and certain others cited therein, deal with monitoring the force being applied to a foot to ascertain the proper force for promoting healing of a patient after hip or knee surgery or injury.
None of the above-cited patents describes a simple system for providing a signal to a person when adverse pressure is applied to any portion of the foot, this adverse pressure potentially causing ulceration. Further, none is specifically designed to be incorporated into special shoes fabricated with relieved inner portions to minimize excess pressure.
Therefore it is an object of the present invention to provide a shoe for use by persons having a foot malady wherein a simple and thus inexpensive monitoring system is utilized to provide a warning to the wearer that excess pressure has been generated at potentially dangerous positions.
Another object of the present invention is to provide a shoe for use by diabetic persons wherein relieved areas are provided in the inner surface of the shoe to reduce pressure at selected regions, with a simple monitoring system associated with these relieved areas to monitor for pressures in excess of those desired in such areas.
It is a further object of the present invention to provide a shoe for use by diabetic persons wherein at least one relieved area is provided in the inner surface of the shoe to reduce pressure at this area, with a force sensing resistor detector being provided beneath the relieved area(s), the force sensing resistor detector being a portion of an electrical circuit such that a signal is generated when excess pressure is detected by the force sensing resistor.
It is also an object of the present invention to provide a shoe for use by diabetic persons wherein at least one relieved area is provided in the inner surface of the shoe to reduce pressure at this at least one area, with a force sensing resistor detector being provided beneath the relieved area(s), the force sensing resistor detector being a portion of an electrical circuit such that a visible signal is instantaneously generated on the outer surface of the shoe when excess pressure is detected by the force sensing resistor.
It is also an object of the present invention to provide a shoe for use by diabetics and other persons with potential detrimental effects of excess pressure against the foot wherein the threshold pressure to cause a warning to the wearer can be adjusted.
These and other objects of the present invention will become apparent upon a consideration of the drawings referred to hereinafter and a complete description thereof.